Profile stitching machines

ABSTRACT

A profile stitching apparatus has a power driven sewing machine and a tracker plate having a slotted profile arranged to be moved with its slot in register with the needle of the machine to sew along the profile. First and second transmission means couple the plate to respective drive means to allow the plate to move relatively to the needle of the machine. The two transmission means each includes a pair of contra-rotatable pinions and an idle gear cooperable with a rack. Each of the transmission means is operable to cause movement of the plate in different directions. The two drive means are independently controlled.

[4 1 Dec. 23, 1975 3,734,038 5/1973 Taketomi....................... Ill/121,15 3,752,098 8/1973 PROFILE STITCHING MACHINES Logan et ll2/l2l.l2

[75] Inventor: George William Palmer, Sudbury,

England Primary Examiner-H. Hampton Hunter [73] Assignee: Stateside Machinery Co., London, Attorney, Agent, or Firm-Edwin E. Greigg England [57] ABSTRACT A profile stitching apparatus has a power driven sew- Feb. 21, 1974 [22] Filed:

21 Appl. No.: 444,682

ing machine and a tracker plate having a slotted profile arranged to be moved with its slot in register with the needle of the machine to sew along the profile.

to respective drive means to allow the plate to move relatively to the needle of the machine. The two transmission means each includes a pair of contra-rotatable [56] References Cited UNITED STATES PATENTS pinions and an idle gear cooperable with a rack. Each of the transmission means is operable to cause movee V fl d 0 w .m

S T. m .m .mmF l m.m u w d 3 t r. CD ys mm .16 m n. .mluelm t C m m .me r 3 OS tn na ee mm US. Patent Dec.23, 1975 Sheet 1 of8 3,927,628

U.S. Patent Dec. 23, 1975 Sheet 2 of8 3,927,628

I I I I I 35L 47- 1 37 LAP-4a US. Patent Dec. 23, 1975 Sheet3of8 3,927,628

U.S. Patent Dec. 23, 1975 Sheet 4 of8 3,927,628

U.S. Patent Dec. 23, 1975 Sheet 5 of8 3,927,628

Sheet 6 of 8 3,927,628

US. Patent Dec. 23, 1975 US. Patent Dec. 23, 1975 Sheet 7 Of8 3,927,628

T0 CONTROL CONSOLE U.S. Patent Dec. 23, 1975 Sheet8of8 3,927,628

CONTROL CONSOLE PROFILE STITCHING MACHINES CROSS REFERENCE TO RELATED APPLICATION This application relates to improvements over those in the copending application of George William Palmer, Ser. No. 408,998, entitled Improvements in and Relating to Profile Stitching Machines, filed Oct. 23, l973, now US. Pat. No. 3,872,807; date Mar. 25, 1975.

BACKGROUND OF THE INVENTION This invention relates to profile stitching machines. The invention relates, more particularly, to profile stitching machines for stitching together two or more layers of material.

In the manufacture of, for example, the collars and cuffs of shirts and similar garments, it is necessary to join together by stitching, at least two layers of material and in order to obtain a satisfactory article, the line of stitching should follow an accurate path and not diverge to any great extent from this path.

To achieve such accuracy, stitching templates or tracker plates are used comprising upper and lower planar members betwen which layers of material to be stitched can be located, a slot having a profile corresponding to the required line of stitching being provided in each planar member and the slots being aligned when the planar members are arranged in superposed relationship to accommodate the needle of a sewing machine allowing the needle to follow the profile of the slots.

As disclosed in the above-mentioned copending application filed on, Oct. 23, 1973, a profile stitching apparatus may include a power driven sewing machine, a stitching tracker plate having a slotted profile arranged to be moved with the slot in register with the needle of the machine to sew along the profile, transmission means arranged to couple the plate to the drive means for the machine to allow the plate to move relatively to the needle of the machine, the transmission means including a gear assembly having a first pair of contra-rotatable pinions cooperable with a rack operatively connected to a first carriage member and arranged to engage guide means arranged along one longitudinal edge of the tracker plate to permit the tracker plate to be moved in a direction transversely of the one longitudinal edge, and the gear assembly including a second pair of contra-rotating pinions cooperable with a second rack operatively connected to a second carriage member arranged to engage further guide means arranged along another lateral edge of the tracker plate to permit the tracker plate to be moved in a direction different from the first mentioned direction, and means included in the transmission means for moving the tracker plate in timed relationship with the operation of the machine such that the tracker plate is moved only when the needle is clear of the workpiece.

The single gear assembly provided in the profile stitching apparatus described above is arranged to provide both East-West movement and North-South movement for the carriage members. Thus, it is not possible, when using the earlier proposed apparatus, to change speed of the movements of the carriage members independently of one another.

Moreover, the speeds provided for the two carriage members of the earlier proposed apparatus are fixed,

2 with respect to the speed of the sewing machine needle. Consequently, the length of stitch could not be varied. The earlier proposed apparatus has a tendency for the needle to become completely unthreaded after the thread iscut at the end of a stitching operation, resulting in undesirable delays so an operator could rethread the needle.

It is an object of the present invention to provide a profile stitching apparatus in which its first and second carriage members can be moved at selected speeds which can be set independently of one another.

It is a further object of the present invention to provide a profile stitching apparatus in which its first and second carriage members can be moved at selected speeds which can be set independently of needle speed so that the length of stitches can be, if desired, varied.

It is an additional object of the present invention to provide a profile stitching apparatus which includes an arrangement which efi'ectively prevents the unthreading of the needle at the end of a stitching operation.

It is another object of the present invention to provide a profile stitching apparatus wherein a template or tracker plate is moved by operation of a sewing machine to allow the needle to stitch along the profile of the template or tracker plate.

It is yet a further object of the invention to provide a profile stitching apparatus wherein a template or tracker plate is moved in response to operation of the sewing machine to allow the needle of the machine to follow the profile of the plate, but only when the needle is in the raised position out of contact with the workpiece.

According tothe present invention, in one aspect, there is provided profile stitching apparatus including a power driven sewing machine having a needle, a stitching tracker plate having a slotted profile arranged to be moved with its slot in register with the needle of the machine to sew along the profile; and first and second transmission means arranged to couple the plate respectively to a first and second drive means to allow the plate to move relatively to the needle of the machine, the first transmission means including a first gear assembly having a first pair of contra-rotatable pinions and a first idle gear cooperable with a first rack means operatively connected to a first carriage member and arranged to engage guide means arranged along one longitudinal edge of the tracker plate to permit the tracker plate to be moved in a direction transversely of the one longitudinal edge, and the second transmission means including a second gear assembly having a second pair of contra-rotating pinions and a second idle gear cooperable with a second rack means operatively connected to a second'carriage member arranged to engage further guide means arranged along another lateral edge of the tracker plate to permit the tracker plate to be moved in a direction different from the first mentioned direction.

In another aspect, the present invention provides an improvement in a profile stitching apparatus or the like which includes a sewing maching having a needle, a top thread tensioning means and thread cutting means, the improvement including thread clamping means positioned in the vicinity of said needle, and means responsive to a signal indicating stopping of said sewing machine for substantially simultaneously clamping the top thread against upward movement and releasing said top thread tensioning means, whereby the needle can be moved upwardly, after cutting of thread, out of a workpiece without the top thread becoming unthreaded from the needle at the end of a stitching operation.

The tracker plate may have first guide means extending along one longitudinal edge of the plate and second guide means extending along one lateral edge of the plate and said first and second guide means being arranged to cooperate with control means associated with the transmission means of the machine to control the relative movement between the tracker plate and the needle of the machine.

In a preferred embodiment of the apparatus the tracker plate guide means comprise upstanding rails extending along one longitudinal edge and one lateral edge of the plate and cooperable with a pair of carriage members having microswitches associated therewith, the tracker plate being moved by the transmission means past the needle and the movement thereof being controlled in response to the actuation of the microswitches.

The pinions are arranged to rotate selectively in response to energization of a respective one of a plurality of clutches; energization of any one of the clutches causing the respective one of the output pinions to rotate to move the rack associated with the pinion.

The transmission means includes intermittent drive means which is arranged to impart intermittent movement to the template or tracker plate to move the plate in timed relationship with the operation of the machine thereby ensuring that the template is moved only when the needle is raised clear of the workpiece. In the proposed profile stitching apparatus, the intermittent drive means includes a modified Geneva gear mechanism having four pins located on a plate integral with an input shaft and arranged to successively engage six slots in a star plate of a Geneva gear; the rotation of the input shaft bringing the pins successively into engagement with the slots in the star plate to effect rotation of the plate in discrete steps to give an intermittent movement thereof. This intermittent motion is transmitted to the gear assembly direction mechanism to control the movement of the tracker plate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of part of a profile stitching apparatus constructed according to the invention disclosed in the above-noted application filed on Oct. 23, 1973.

FIG. 2 is a plan view of the carriage drive mechanism and the geneva gear mechanism for intermittent movement of the tracker plate in the apparatus shown in FIG. 1.

FIG. 3 is a section of the carriage drive mechanism taken along the line 3-3 of FIG. 2.

FIG. 4 is a section of the Geneva gear mechanism taken along the line 4-4 of FIG. 2.

FIG. 5 is a section taken on the line 5-5 of FIG. 1 of part of the profile stitching mechanism showing the thread cutting mechanism beneath the needle plate of the machine.

FIG. 6 is a plan view of the thread cutting mechanism of FIG. 5.

FIG. 7 is a block schematic diagram of the control circuitry for the profile stitching mechanism showing the interrelationship between the various components thereof.

FIG. 8 is a perspective view of the tracker plate.

FIG. 9 is a section taken on the line 9-9 of FIG. 8.

FIG. 10 is a perspective view of a profile stitching apparatus according to the present invention.

FIG. 11 is a plan view of a carriage drive mechanism suitable for use as the carriage drive mechanism suitable for use as the carriage drive mechanism in the apparatus shown in FIG. 10.

FIG. 12 is a perspective, partially diagrammatic view of an arrangement for preventing the unthreading of thread from the needle in the apparatuses shown in FIGS. 1 and 10.

FIG. 13 is a cross-sectional view taken along section line 13-13 in FIG. 12.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to the drawings, a sewing machine 1 has a machine head 2 of conventional type containing a mechanism for effecting reciprocatory movement of a needle 3 (FIG. 5) to perform a sewing function in conjunction with a thread carried by a shuttle arrangement located beneath the working surface of the machine. The needle 3 is driven from an electric motor 4 (FIGS. 1 and 7) coupled to the needle driving mechanism (not shown) through a main transmission which includes a clutch/brake unit 5 through which power from the electric meter 4 is transmitted to the machine 1. A template drive mechanism which imparts movement to a stitching template 6 located on the working surface of the machine, is connected to the main transmission shaft coupled through a drive means 8 to the output shaft of the clutch/brake unit 5.

The template transmission includes an intermittent drive mechanism 9 (FIGS. 1, 2 and 4) which is arranged to impart intermittent movement to the template 6 to synchronize the movement of the template 6 with themovement of the needle 3 so that the template is moved only when the needle is clear of the material being stitched.

The intermittent drive means 9 comprises a Geneva type mechanism (FIG. 4) having an input shaft 13 driven by a take off drive means 10 from the main transmission shafft 7. Four pins 11 are located on a plate 12 formed integrally with the shaft 13 and equidistantly spaced around the periphery with their polar axes parallel to the axis of the shaft 13. As the shaft 13 is rotated, each of the pins 11 engages in turn with one of six slots 14 in a star plate 15 of the Geneva mechanism which is mounted for rotation about an axis 16 parallel to, but spaced from the axis of rotation of the input shaft 13. The arrangement operates in the usual manner of a Geneva mechanism in that as the input shaft 13 is rotated, the pins 11 are brought successively into engagement with the slots 14 in the star plate 15 to rotate the star plate in steps to thereby give an intermittent output.

The star plate 15 is connected to the input shaft of a direction gear box 17 by means of shaft 18 and univer- Sal-couplings 19, 20; the gear box 17 controlling the direction of movement of template 6 so that the template is also moved intermittently.

A disc 21 which serves as a light shield is mounted on the input shaft 13 of the Geneva mechanism for rotation therewith, the disc 21 having two orifices 22, 23, arranged at diametrically opposite points of the disc 21. A light source 24 mounted on the machine body is positioned on one side of the disc 21, the light from the source being arranged to pass through one of the orifices e.g. 22 as shown in FIG. 1, to irradiate a light sensitive device 25, located on the other side of the disc 21 remote from the source 24. The light sensitive device 25, when irradiated; produces a signal which overrides the control of the main motor 4 and the clutch/- brake unit 5; the orifices 22, 23, being arrangedsuch that the light sensitive device 25, is operated to ensure that when the clutch isdisengaged, the transmission is brought to a standstill with the needle 3 in the raised position clear of the tracker plate 6.

The direction gear box 17 (FIG. 2) has a first pair of contra-rotating output shafts 26, 27, the axes of which lie in a first plane, and a second pair of contra-rotating output shafts 28, 29, the axes of which are in the same plane as and normal to the axes of the first pair of shafts 26, 27. The shaft 18 is universally coupled to the input shaft 30 of the direction gear box via coupling 20 and shaft has pinion 31 located thereon arranged to mesh with intermediate pinion 32 which meshes with pinion 33 of a reduction gear train; Pinion 33 is mounted on shaft 34 which has a further pinion 35 thereon'arranged to mesh withpinion 36 mounted on an output shaft 37 which is parallel to and spaced from shaft 34; the pinion 36 thus rotating in the opposite direction from that of pinion 35.

The second pair of output shafts 28, 29 are driven through bevel gears 38, 39 on shafts 34, 40 respectively and meshing pinions 41, 42 in a similar manner to the first pair of output shafts 26, 27. Each output shaft 26, 27; 28, 29; has associated therewith a respective output pinion 43, 44; 45, 46; which is arranged to be operatively coupled to the respective output shaft 26, 27; 28, 29; to effect rotation thereof in response to the energisation of the winding of a respective electromagnetically operable clutch 47, 48; 49, 50. Each pair of output pinions are pennanently meshed with a respective rack 51, 52, and the racks lie normal to one another in a horizontal position below the working surface of the sewing machine as shown in FIG. 1.

' Since the output pinion 43, 44 are both permanently meshed with the rack 51, it follows that the clutch 47, 48 of one only of each pair of output shafts 26, 27; 28, 29; may be energised at any one time so that only one output pinion e.g. 43, 45, of each pair-may be driven by the main transmission at such time. When one pinion e.g. 43, is being driven, the other pinion 44 of the pair is rotated in the samesense through the rack 51 and thus rotates freely on its output shaft 27 Thus, by selective energisation of the clutches 47 48; 49, 50; the racks 51, 52, may be each moved to and fro along a path aligned with the respective longitudinal axes of the racks;

Each rack 51, 52, is connected through a linkage 53, 54 respectively to a carriage 55, 56, mounted above the work surface, the carriages 55, 56, each being adapted to engage with an associated guide rail 57, 58 respectively on the template 6 (see also FIGS."8 and 9). The work surface has therein a pair of slots 59, 60, one normal to the other through which the linkages 53,- 54, project. Thus movement of the racks 51, 52, caused by rotation of the output pinions '26, 27; 28, 29; is transmitted through the respective linkages to the carriages 55, 56 and the'template 6 located on top of the working surface. I

The carriages 55, 56 comprise a control carriage 56 for moving the template 6 'in a first path and a side carriage for moving the template 6 ina path normal to the first path. Each carriage comprises a main body 61, 62 carrying at least one pair of guide wheels 63, 64;

65, 66 mounted with their axes of rotation vertical, the

wheels of any pair being adapted to engage one on each side of a respective guide rail 57, 58 of the template 6 so that the carriage 55, 56 may move freely along the length of the guide rail 57, 58 but when moved horizontally normal to the length of the guide rail will, by virtue of engagement of the wheels 63, 64; 65, 66 with the guide rails move the guide rails and hence the template 6.

Microswitche's M/Sl, M/S2 (FIG. 7) mounted on the carriages have the contacts in engagement with the guide rails 57, 58 on the template 6, the contacts of the microswitches being held by the respective rail against the bias to the open position when so engaged, when the carriages are in engagement with their respective guide rails.

The main body 62 of the control carriage 56 is pivotable between a raised and lowered position. A reset microswitch M/S3 mounted on the carriage 56 is operated by the pivotal movement of the main body 62, for a purpose hereinafter defined.

The template 6 comprises a pair of rectangular plates 67, 68 connected one to the other through a hinge 69 adjacent one longitudinal edge. Thus, the plates 67, 68

' are pivotable to an open position to enable the layers of material 69 (FIG. 5) to be stitched together to be placed therebetween, the plates 67, 68 being pivotable to a closed position to locate the material to maintain it in the correct position within the template 6. Each of the plates 67, 68 has a slot or track 70, 71 defining the path and profile required for the stitching of the material, the slots 70, 71 being aligned when the template 6 is in the closed position. The slot 71 in the lower plate 68 is adapted to engage with a guide device which comprises a raised tubular element 73 projecting from the working surface of the sewing machine 1 and arranged concentrically with the needle 3 to thereby locate the template 6, and hence the path and profile to vbe stitched, relative to the needle. The cotton (not shown) from the shuttle (not shown) mounted beneath the working surface passes up through the bore of the guide device 73, which is rotatable in bearing member 73a.

Guide members 75, 76 extend outwardly from two adjacent sides of the template 6 to lie in the same plane as the lower plate, the guide members extending over the length of the respective sides. The guide rails 57, 58 extend along the length of the outer edge of each of the guide members, and extend upwardly normal to the plane of the guide members 75, 76. Thus, the guide rails 57, 58 are normal one to the other. The longer guide rail 58 is adapted to be engaged by the control carriage 56 and the shorter guide rail 57 by the side carriage 55.

The guide rails 58, 57 each have a number of notches 77, 78 formed along the upper edges thereof notches allowing the contacts of the microswitches M/Sl, M/S2 mounted on the carriages to be actuated. Thus, when a microswitch e.g.' M/Sl is aligned with a notch e.g. 77 the contacts of the microswitch which are normally open are closed since the contacts are no longer held open against the bias by the guide rail 58.

The operation of the sewing machine is controlled through an electrical control circuit (FIG. 7). Current for the control circuit is obtained via line 80 from the mains supply which is supplied to a transformer 81 arranged to give a 24 volt output. The output of the transformer is fed to a rectifier 82 to provide a low voltage DC output on line 83. The DC output is passed through a capacitance smoothing circuit (not shown) to provide a steady 24 volt DC for the control circuit.

The microswitches M/Sl, M/SZ on the carriages 55, 56, are connected in series so that before the electrical circuit can be completed the contacts of both the microswitches M/Al, M/SZ must be closed and thus, the control circuit is not completed until both carriges 55, 56 are in predetermined positions relative to the template guide rails 57, 58.

When the contacts of both the microswitches M/Sl, M/S2 are closed, the DC. level on line 83 changes and pulses are produced by a pulse generator of a sequential unit 84 which also includes a decade counter. The two microswitches M/Sl, M/SZ are arranged as an AND gate and the pulses are applied direct to the decade counter, the output signal of which is then transferred to a binary coded decimal decoder which in turn feeds ten transistor amplifiers to give a ringcount of 10. The decade counter and decoder are preferably both monolithic integrated circuits of the transistor/- transistor logic type. A reset line R is connected to a built-in feature of the counter and a pulse transmitted therealong overrides all stored information in the sequential unit 84 and resets the counter instantly to stage 1. The reset line R is connected directly to the reset microswitch M/S3 on the control carriage 56. Output signals from the sequential unit 84 are supplied via programme selector unit 85 to a direction control unit 85a and also to module D which includes a thyristor D1 which is fired when the thyristor trigger receives an output signal from the sequential unit 84 in a selector unit 85 when the counter thereof is reset to stage 1. The firing of the thyristor D1 causes an output signal to be sent before the contacts of M/S4 move to the position shown via line 86 to effect energisation of a drop solenoid 87 associated with control carriage 56, thereby allowing a spring latch to be released by actuation of the armature to cause the control carriage 56 to pivot downwardly into engagement with the tracker plate 6. When the control carriage 56 is lowered, contacts of a double pole microswitch M/S4 are actuated to move into the position shown and remove current from the winding of the drop solenoid to prevent overheating thereof and cutting off the thyristor D1 of module D and making power available to the electromagnetic clutches 47, 48; 49, 50; of the directional gear box 17 as will be described hereinafter.

The output signal derived from the last step of the sequential unit 84 is arranged to supply a finish signal to the module D via programme selector unit 85 to trigger a second thyristor D2 which then provides an output signal for energisation of the winding of a lift solenoid 88 on the control carriage 56 to cause the main body of the control carriage 56 to be lifted from engagementwith the template 6. Lifting of the carriage 56 causes actuation of the contacts of a double pole microswitch M/SS previously in the condition shown in FIG. 7 to supply a stop signal to the clutch/brake unit to disconnect the driving clutch and apply the braketo stop the machine. When the main body of the control carriage 56 is lifted to the raised position by energisation of the solenoid 88, the contacts of the microswitch M/S4 are actuated to cut off power to microswitches M/Sl, M/S2 and to the solenoid 88 to prevent overheating thereof. A spring latch which engagesautomatically when the carriage is lifted, maintains the carriage in the raised position.

The programme unit is a plug-in module on the control panel of the machine and includes a diode matrix which receives pulses from the sequential unit 84 and is connected to the direction control unit 850. The latter unit includes four power transistors connected in circuit with a capacitor/resistor network to give a predetermined time delay in accordance with the time constant of the circuit when each transistor is triggered. Each transistor controls a respective one of the electro-magnetically operable clutches 47, 48; 49, 50; in the direction gear box 17. Thus the outputs from the sequential unit 84 are arranged to render conductive selected diodes of the matrix. The particular diode or diodes rendered conductive is/aredetermined by the wiring of the matrix and this is determined by the sequential movements required for the template to follow the profile of the slot on the particular template used. Thus, an output signal originating from the sequential unit 84 is directed to the appropriate power transistor of the direction control unit 85a via the programme unit matrix. The R/C time delay at the time of stitching enables the machine to form two or more stitches in the corners of the work being sewn.

The programme selector unit 85 is designed as a plug-in unit and thus when a different template is used having a differently profiled slot, an appropriate programme selector unit 85 must be plugged into the machine as shown in FIG. 1.

In certain circumstances, not all the steps of the sequential unit 84 are required to perform a particular operation and a programme advance switch 89 is mounted on the control carriage 56; operation of which sends a pulse to the sequential unit 84 to step the sequential unit round one step. The programme advance switch 89 operates a pulse generator the required number of times to step the unit round to its starting position i.e. stage 1 and a feed back signal holds the sequential unit until microswitch M/S4 is activated upon the dropping of the carriage. Indicating lamps I are provided on a control panel on the sewing machine to indicate which step of the sequential unit is in circuit.

Thus, when the counter of the sequential unit 84 is stopped a signal is not only sent to the programme unit 85, but also an indicator lamp is illuminated on the control panel I to provide a digital read out at 90. The read out provides an indication of the stage at which the machine is.

All of the units of the circuit are arranged to be plugin units so that if a fault occurs in a particular unit it may be replaced by spare units to enable the machine to continue in use while the faulty unit is being repaired.

The operation of the above described embodiment is as follows:

The guide member 73 of the needle plate engages in the slots in the tracker plate 6. In the off position of the sewing machine. the control carriage 56 is held in the raised position by means of an arm (not shown). The material 69' to be stitched is located between the plates 67, 68 of the template 6 and the template is placed under the control carriage 56 with the slots located over the guide member 73. When the template 6 is in the correct position for the commencement of a machining cycle. the contacts of the reset microswitch M/S3 are closed. A circuit is completed to the sequential unit 84 (before the contacts of switch M/S4 move to the position shown) to cause the counter to be reset to the first counting position. The sequential unit in this 9 position sends an output signal to thyristor D1 of module D which controls the supply of power to the drop solenoid 87.

When the winding of the drop solenoid 87 is energised, the armature thereof is moved against a spring bias causing the spring latch which holds the control carriage in the raised position, to be moved into align ment with a recess in the control carriage to allow the control carriage 56 to drop to the operative position. When the control carriage 56 is lowered, the contacts of the microswitch M/S4 are actuated to remove current from the winding of the drop solenoid 87 to prevent overheating thereof as previously described.

The actuation of switch M/S4 also cuts off the thyristor D1 of module D and makes power available to all the electro-magnetic clutches 47, 48; 49, 50; of the directional gear box 17.

The microswitches M/Sl, M/S2 on the carriages 56, 55 respectively are connected in series and when the contact of both switches are closed on alignment with the V-shaped notches in the guide rails of the template, a signal pulse is supplied to the sequential unit 84 to advance the counter'thereof by one step. The stepping of the counter by one step causes a pulse to pass through the diode matrix of the programme unit85 to the direction control unit 85a, which provides a current path to a preselected one or two of the windings of the clutches 47, 48; 49, 50; of the direction gear box 17. Thus, for example if it is desired to move the template 6 in one direction only then only one of the windings of the clutches will be energised to couple the associated output pinion to the main transmission. Thus, the template 6 will be moved in the selected direction by rotation of the pinion, which motion is transferred to the associated rack 51, 52, and hence through the linkage to the appropriate carriage. Since the second output pinion of the pair is meshed with the rack it will be rotated by the rack and thus if it is required to reverse the direction of movement of the template 6, when the first clutch is de-energised and the second clutch is energised to reverse the direction, there will be no backlash to be taken up before the direction of movement of the template is changed. If during this second step it is desired to move the template 6 in both paths then the windings of two clutches are energised; one from each of the pairs of clutches. Thus if the template is required to move at, for example, an angle of 45 relative to the paths then the windings of two clutches will be energised. It will be appreciated that when moving in this direction and particularly when moving round a curve of varying radius, then the amount of movement required in a given direction may vary nonlinearly with time. To enable this to take place the coupling forces of the clutches are arranged to be sufiiciently small that when a resisting force is applied by virtue of the template being restrained from movement in said direction then the clutches will slip until said retarding force is removed. The actual path of movement of the template 6 is determined by the slot which is always engaged with the guide device 73 located concentrically with the needle. Thus minor variations in direction, such as following a shallow curve are controlled by the slot, the template drive transmission merely pulling or pushing the templatc is a straight line along the path required.

Just before the end of a machining cycle, the last pulse from the sequential unit is arranged to fire the thyristor D2 of Module D to energise the winding of the 10 lift solenoid 88 on the control carriage 56. There'is a slight time lag in the response of the solenoid 88 and therefore the winding of the solenoid 88 is energised a sufficient time before the end of the cycle to enable the cycle to be completed before the solenoid responds to lift the carriage 56 from the template 6.

When the control carriage 56 is lifted up the spring latch automatically locates in a slot provided in the control carriage 56 to maintain the carriage in the raised position. Simultaneously the contacts of the microswitch M/S4 are opened to cut off power to the solenoid 88 to prevent over heating of the solenoid.

When the control carrige 56 is lifted the change-over microswitch M/SS is also operated to de-energise the windings of the clutches and actuate the brake 5 to the on position to bring the machine to a standstill. As described previously the light sensitive device is arranged to ensure that the machine is stopped with the needle in the raised position and thus the brake 5 is actuated to the on position only when the light sensitive device 25 is irradiated.

If the light sensitive device is not irradiated, there is release of the brake and a reduced current is switched back to the windings of the clutch again under the control of Module E and a slipping clutch effect is achieved.

Module E comprises a transistor pair operating as a bistable switch arranged to operate only when the contacts of microswitch M/S5 are closed i.e. when the carriage is lifted. The bistable switch is controlled in response to output signals from the photo-sensitive device 25. When the device 25 is irradiated, the drive switches from slipping clutch to the brake and vice versa. The brake is then actuated and halts the machine operation with the needle raised. Four potentiometers P1, P2, P3, P4 are included in circuit between the outputs of the direction control unit a and the windings of the clutches 47, 48; 49, 50; to obtain a consistent stitch in all directions; the potentiometers reducing the power available to the clutches to vary the stitch length. An overall change of stitch length is effected by replacing pinion 33 (FIG. 2) with another pinion having a predetermined number of teeth. A spring-loaded ball (not shown) is provided for retaining pinion 33 on shaft 34 outside the gear box to allow quick and easy overall variation of stitch length.

, The machine may include a cutter to automatically cut the thread passing through the needle 3 (FIG. 5) when the template is withdrawn. The cutter apparatus comprises a scissors arrangement (FIG. 6) including pivoted blades 100, 101 mounted on the needle plate 102 and operated by a solenoid 103 (FIG. 7) through a Bowden type cable 104 (FIG. 6).

The scissors arrangement includes lever 100, pivotally mounted intermediate its length on the underside of the throat plate 102. The lever has longitudinally extending slots 105, 106 on either side of the pivotal mounting 107, one of which slots 105, is engaged by an upstanding pin 108 located on the second lever 101. The second lever 101 is pivotally mounted at 109 adjacent one end, on the underside of the throat plate 102 and has the cable 104 connected thereto on the side of the pivotal mounting remote from the upstanding pin 108. The cable 104 is connected to the armature of the solenoid 103 such that energisation of the solenoid winding causes the cable to urge the lever 10] about the pivot 109. The winding of the solenoid 103 is energised via relay 110 from the signal which 1 1 controls the de-energisation of the clutch and the actuation of the main brake 5 at the termination of a machining cycle.

Module M (FIG. 7) controls the energisation of the winding of relay 110 (module M). The line from the microswitch M/SS is positive and the voltage thereon is applied via a diode which bypasses thyristor D3 of Module N to charge a capacitor. A transistor circuit with a resistor/capacitor time delay effects the firing of thyristor D3 which discharges the capacitor through the relay coil 110 and back to the microswitch M/S5 line which goes negative when the brake is applied. Two conditions must be fulfilled to enable the relay winding to be energised:

a. the machine must be stopped with the needle in the raised position which means that the brake will have been applied. Thus the microswitch M/SS line will be at negative potential to accept the capacitor discharge referred to above b. a signal from the sequential unit 84 is directed via the matrix of programme unit 85 to the base of the thyristor D3 triggering transistor, at the end of the sewing cycle. The resistor/capacitor delay on the trigger transistor is to ensure that the needle has definitely stopped on the raised position and is not ready to recycle via the slipping clutch. The thyristor provides sufficient delay for the cutting operation to be effected together with the delay provided by the time constant of the capacitative discharge circuit. The thyristor D3 is fired only when the needle is in the raised position. The capacitor discharges to supply energising current to the winding of the relay 1 10 to effect energisation of the winding of solenoid 103. This causes the second lever 101 to pivot and the upstanding pin 108 moves through an arcuate path to pivot the first lever 100 in the opposite direction from that of lever 101, thus providing a scissors movement. The scissors action is arranged to take place across the path of the thread to enable the template 6 to be withdrawn from the machine. A coil spring is wound concentrically about the pivot pin 109 and is arranged to bias the scissors levers 100, 101, to open position. Lever 101 is set to measure the required length of thread necessary at the shuttle to enable the needle to pick up the thread on the next cycle. Lever 100 which has a delayed action caused by the action of the upstanding pin 108 in the slot 105, cuts the thread close to the needle plate 102 at the end of its travel.

It is to be appreciated that the apparatus as so far described has been described by way of example only and is capable of considerable modification. For instance, the counter of the sequential unit 84 may be extended by providing a pair of relays each having four change over poles and arranged to be switched at the end of a counting sequence to add eight further counting stages if required. The sequential unit would have a count of 18 and the operation of the relays would be controlled in response to the firing of a thyristor in Module N.

An illustrative embodiment of a profile stitching apparatus according to the present invention is shown in FIG. 10, parts of which correspond to similar parts shown in FIG. 1 being provided with corresponding identical reference numerals. Since those parts of FIG. 10, designated by reference numerals and letters which correspond to numerals and letters of FIG. 1, represent parts having corresponding constructions, functions 12 and placements, it does not appear necessary to discuss them all in detail.

Unlike the profile stitching apparatus shown in FIG. 1, the profile stitching apparatus illustrated in FIG. 10 is not provided with a single intermittent drive mechanism (9, FIG. 1) of the Geneva type, a single gear box (17, FIG. 1) and take-off drive means (10, FIG. 1) from a main transmission shaft 7.

The profile stitching apparatus illustrated in FIG. 10 includes a first directional gear box which is internally provided with a first gear assembly, having an idle gear 111 which engages the rack 51 which lies normal to the rack 52. A second directional gear box 112 is internally provided with a second gear assembly, having an idle gear 113. The idle gear 113 engages the rack 52.

A fractional horse-power motor, a universal joint,

reduction gears and electromagnets are provided within each of the gear boxes 1 10 and 112, the arrangement being shown in detail in FIG. 11 which is to be described in detail hereinafter. Each of the gear boxes 110 and 112 is advantageously associated respectively with a respective microswitch M/S 110, M/S 112 which cooperate with stops (not shown) to effect the deenergization of the respective motors in the gear boxes 110 and l 12 whenever the gear boxes 110 or 112 have provided movement to given maximum positions.

The sewing machine includes a flywheel 114 having at least one magnet 115 positioned in the vicinity of its outer periphery. A reed switch 1 16 or the like is fixedly positioned in proximity to the outer periphery of the flywheel 1 14 so as to sense the positioning of the needle 3 of the sewing machine. The magnet 115 is so positioned about the periphery that its position opposite the reed switch 116 occurs whenever the needle 3 is in its raised position, the reed switch 116 providing a signal on a line 117 which overrides the control of the main motor 4 and the clutch/brake unit 5. The signal from the line 1 17 is fed to a console which, in response to the signal on the line 117 and a signal indicating the end of a stitching operation, provides a control signal which de-energizes the motor 4. Thus, the motor 4 can be de-energized only when the needle 3 is in its raised position clear of the tracker plate 6.

The console 1 18 includes a plug-in programme selector unit 119, which corresponds to the programme selector unit 85 shown in FIG. 1, but is preferably made of integrated circuits. The console 118, as illustrated, includes three knobs 120, 121 and 122 for the purpose respectively of adjusting needle position, East-West stitch length and North-South stitch length. It is to be understood that the control knobs -122 may be positioned at some point other than on the console I 18. The console 118 is provided with a plurality of signal lights 123 which indicate the direction of movement of the carriage members at any given operational time, and with a digital display means 124. The digital display means 124 can display, for example, a numeral or numerals to indicate the stage the stitching operation is currently undergoing.

It is to be appreciated that the programme selector unit 119, in conjunction with the individual motors and electromagnets within the gear boxes 110 and 112 effect movement of the template 6, the speed of the motor within the gear box 110 being set by the knob 121 and the speed of the motor within the gear box 1 13 beingset by the know 122.

Referring to FIG. 11, a gear box arrangement suitable for use as the gear box 110 (FIG. is shown in conjunction with a speed control 125 and the knob 121 which is used to set the speed of a fractional horse power electric motor 126 which is advantageously placed within the gear box 110. The motor 126 is mechanically coupled, via universal joints 127 and reduction gears 128 to a gear 129 which drives a gear 130, the gears 129, 130 being fixed to their respective shafts to provide for contra-rotating movements.

A pair of pinions 131, 132 are fixed respectively to axially movable clutch members through which the respective clutch shafts 133 and 134 extend. Each of the pinions 131 and 132 is meshed with the idle gear 111, also shown in FIG. 10, which contacts the rack 51 (FIG. 10). A pair of electromagnetic clutches 135, 136 are positioned respectively in proximity to the clutch shafts 133, 134, the electromagnetic clutches 135, 136 being provided with input electrical connections from the control console 118 (FIG. 10) so as to be energized therefrom in accordance .with a programme provided by the programme selector unit 119.

The gear box also includes mechanical clutch members 137, 138 which are positioned respectively between the pinions 131, 132 and the electromagnetic clutches 135, 136.

In operation, signals from the console 118 (FIG. 10 energize selectively the electromagnetic clutches 135, 136 to provide respective movement of the workpiece in the West and East directions. When the electromagnetic clutch 135 is energized, the clutch member 137 effects coupling between the clutch shaft 133 and the pinion 131, resulting in the rotation of the pinion 131 which drives the idle gear 111. Since the idle gear 111 meshes with the rack 51, the workpiece is moved to the West. When the electromagnetic clutch 136 is energized, the idle gear 111 is rotated in its opposite direction, the idle gear 111 being driven by the pinion 132 which rotates because of coupling between the clutch shaft 134 and the pinion 132.

Since the gears 129 and 130 are constantly meshed, the drive system is substantially free of backlash.

It is to be appreciated that the gear box 112 is internally constructed identically to the gearbox 110, the only differences being that its idle gear 113 (FIG. 10) contacts the rack 52 (FIG. 10) and that its two electromagnets are selectively energized from the console 118 in accordance with a different portion of the programme provided from the programme selector unit 119. Thus, it is not necessary to discuss the interval construction details of the gear box 112. Energization of the representative electromagnets within the gear box 112 result respectively in movement of the workpiece in South and North directions.

Referring to FIGS. 12 and 13, the neddle 3 of the sewing machine forming part of a profile stitching apparatus is threaded with a thread 140 supplied from a spool (not shown), the thread running from the spool via a pair of tension discs 141, and guide 142 and an eye 143. The eye 143 is fixedly connected to a take-up arm 144. Upon completion of a stitching operation, the take-up arm 144 moves the needle holder, which holds the needle 3 upwardly, the thread having been cut by a cutting device (not shown in FIGS. 12, 13).

A clamp arm 145 is pivotably mounted at point 146, a spring 147 being provided for biasing the clamp arm 145 so as to force a clamp 148, carried by the clamp arm 145, against the thread 140 whenever the thread is cut at the completion of a stitching operation. A solenoid 149, which is energized during stitching operations, has its armature mechanically coupled, via linking member 150, to the clamp arm 145, its point of connection being displaced from the pivotal mounting point 146 so that upon energization of the solenoid 149 the arm is moved against the force of the spring 147, and the clamp 148 removed from contact with the thread 140.

The pair of tension discs 141 are advantageously spring biased by spring means (not visible) so that the discs 141 are held apart during times when no forces are exerted on the discs 141 by the solenoid 149. Whenever the solenoid 149 is energized, which is during periods when stitching takes place, its armature 151 connected directly to one of the discs 141 as indicated diagrammatically by a dashed line overcomes the spring bias holding discs 141 apart. As a result, whenever the solenoid 149 is energized, the tension discs 141 contact the thread 140 running between them, resulting in an appropriate thread tension'.

At the end of a stitching operation, a cutting device (not shown in FIGS. 12, 13) receives a signal from the console 118 (FIG. 10) and severs the top and bottom threads at some distance before the needle 3. The solenoid 149 is deenergized resulting in the clamp 148 contacting the top thread 140 and holding it against possible movement out of the eye of the needle 3. At the same time, the tension discs 141, under action of spring biasing means (not visible in FIG. 12), are moved apart, releasing thread tension in the thread 140. Consequently, the take-up arm 144 can move the needle holder upwardly out of contact with the workpiece and above the plate 6 (FIG. 10).

It is to be understood that the preferred embodiments discussed above do not involve any means, such as a Geneva drive, for driving the first and the second transmission means to effect movement of the tracker plate in timed relationship with the operation of the sewing machine so that the tracker plate is moved only when the needle is clear of the workpiece.

It is to be appreciated that the foregoing discussion of the preferred embodiments of the invention and accompanying drawing figures have been provided by way of example. Numerous variants and other embodiments are possible without departing from the spirit and scope of the invention, the scope being defined in the appended claims.

That which is claimed is:

1. A profile stitching apparatus including a power driven sewing machine having a needle, a stitching tracker plate having a slotted profile arranged to be moved with its slot in register with said needle of said sewing machine to sew along said profile; and first and second transmission means arranged to couple said plate respectively to a first and to a second drive means to allow said plate to move relatively to said needle of said sewing machine, said first transmission means including a first gear assembly having a first pair of contra-rotatable pinions each of which engages a first idler gear meshed with a first rack means which, in turn, is operatively connected to a first carriage member and arranged to engage guide means arranged along one longitudinal edge of said tracker plate to permit said tracker plate to be moved in a direction transversely of said first longitudinal edge, and said second transmission means including a second gear assembly having a second pair of contra-rotating pinions each of which engages a second idle gear meshed with a second rack means which, in turn, is operatively connected to a second carriage member arranged to engage further guide means arranged along another lateral edge of said tracker plate to permit said tracker plate to be moved in a direction different from the first mentioned direction.

2. An apparatus as claimed in claim 1, including a first electric motor coupled to said first gear assembly for driving said first gear assembly, and a second electric motor coupled to said second gear assembly for driving said second gear assembly.

3. An apparatus as claimed in claim 2, including adjustable control means for setting speed of at least one of said first and second electric motors.

4. An apparatus as claimed in claim 3, wherein said adjustable control means includes a first control means for adjustably setting speed of said first electric motor, and a second control means for adjustably setting speed of said second electric motor.

5. An apparatus as claimed in claim 1, wherein said tracker plate has first guide means extending along one longitudinal edge of said plate, and second guide means extending along one lateral edge of said plate, said first and second guide means being arranged to cooperate with control means associated with said first and second transmission means of said machine to control relative movement between said tracker plate and said needle of said machine.

6. An apparatus as claimed in claim 1, wherein each of said pinions is arranged to rotate in response to the energization of a winding of a respective electromagnetic clutch, said pinion being couplable respectively to respective ones of said clutches such that energization of the winding of any of said clutches effects rotation of the respective one of said pinions to move that one of said rack means associated therewith.

7. An apparatus as claimed in claim 1, including means for determining the instant position of said needle for developing a control signal, said means for permitting movement of said tracker plate being controllably associated with said means for determining and responsive to its output.

8. An apparatus as claimed in claim 1, wherein each carriage member includes at least one pair of guide wheels mounted with their axes of rotation vertical and arranged to engage one on each side of the respective said guide means of said tracker plate to allow said carriage members to traverse the length of the respective said guide means.

9. An apparatus as claimed in claim 1, wherein each said guide means on said tracker plate is provided with a plurality of notches and each said carriage member is provided with a respective switch member, the contacts of which are arranged to be closed whenever the respective switch member of a particular said carriage member is aligned with a notch on the respective one of said edges of said tracker plate.

10. An apparatus as claimed in claim 9, wherein said first carriage member includes a main body portion pivotable between a raised and lowered position, this carriage member being provided with a further switch member whose contacts are actuated when the main 16 portion of said first carriage member is raised or lowered.

11. An apparatus as claimed in claim 9, wherein said switch members comprise first and second microswitches provided on said first and second carriage members respectively, said first and second microswitches being connected electrically in series and to a sequencing unit, which includes counting means arranged to be stepped sequentially in response to pulses generated each time contacts of said first and second microswitches are actuated upon alignment of said switches with notches in said guide means of said tracker plate.

12. An apparatus as claimed in claim 11, including a further switch member, and wherein contacts of said further switch member are actuated whenever said tracker plate is in the correct position for commencement of a machine cycle, to complete a circuit to a sequencing unit to reset its counting means to the beginning of a counting cycle, said sequencing unit including a trigger delay circuit being repsonsive to the resetting of said sequencing unit to supply energizing current to a winding of a solenoid associated with said first carriage member, an arm connected to an armature of said solenoid retaining said first carriage member in its raised position and energization of said winding of said solenoid effecting actuation of said armature to actuate said arm and allow said first carriage member to move into engagement with said tracker plate.

13. An apparatus as claimed in claim 12, wherein said winding of said solenoid is de-energized upon movement of said first carriage member and power is supplied to electromagnet clutch means associated with one of said gear assemblies.

14. An apparatus as claimed in claim 13, including a plurality of electromagnetic clutches, and stepped counting means for supplying an output pulse via a matrix of a programme unit to a control means providing a preselected current path to at least one of said electromagnetic clutches of said gear assemblies to effect energization of the winding thereof and to cause a respective one of said pinions to be rotated to move the associated rack via one of said idle gears.

15. An apparatus as claimed in claim 1, including a thread cutting device provided on said machine beneath the needle plate thereof, said device including a solenoid whose winding is energized in response to application of a brake to cut the thread and allow said tracker plate to be removed from the machine.

16. An apparatus as claimed in claim 15, including means responsive to stopping of movement of said tracker plate to hold thread in said needle to allow said needle to be withdrawn from the workpiece without dethreading.

17. A profile stitching apparatus as claimed in claim 1, wherein additional means, associated with said first and second transmission means, are provided for permitting movement of said tracker plate in timed relationship with the operation of said sewing machine such that said tracker plate is moved only when said needle is clear of a workpiece. 

1. A profile stitching apparatus including a power driven sewing machine having a needle, a stitching tracker plate having a slotted profile arranged to be moved with its slot in register with said needle of said sewing machine to sew along said profile; and first and second transmission means arranged to couple said plate respectively to a first and to a second drive means to allow said plate to move relatively to said needle of said sewing machine, said first transmission means including a first gear assembly having a first pair of contra-rotatable pinions each of which engages a first idler gear meshed with a first rack means which, in turn, is operatively connected to a first carriage member and arranged to engage guide means arranged along one longitudinal edge of said tracker plate to permit said tracker plate to be moved in a direction transversely of said first longitudinal edge, and said second transmission means including a second gear assembly having a second pair of contrarotating pinions each of which engages a second idle gear meshed with a second rack means which, in turn, is operatively connected to a second carriage member arranged to engage further guide means arranged along another lateral edge of said tracker plate to permit said tracker plate to be moved in a direction different from the first mentioned direction.
 2. An apparatus as claimed in claim 1, including a first electric motor coupled to said first gear assembly for driving said first gear assembly, and a second electric motor coupled to said second gear assembly for driving said second gear assembly.
 3. An apparatus as claimed in claim 2, including adjustable control means for setting speed of at least one of said first and second electric motors.
 4. An apparatus as claimed in claim 3, wherein said adjustable control means includes a first control means for adjustably setting speed of said first electric motor, and a second control means for adjustably setting speed of said second electric motor.
 5. An apparatus as claimed in claim 1, wherein said tracker plate has first guide means extending along one longitudinal edge of said plate, and second guide means extending along one lateral edge of said plate, said first and second guide means being arranged to cooperate with control means associated with said first and second transmission means of said machine to control relative movement between said tracker plate and said needle of said machine.
 6. An apparatus as claimed in claim 1, wherein each of said pinions is arranged to rotate in response to the energization of a winding of a respective electromagnetic clutch, said pinion being couplable respectively to respective ones of said clutches such that energization of the winding of any of said clutches effects rotation of the resPective one of said pinions to move that one of said rack means associated therewith.
 7. An apparatus as claimed in claim 1, including means for determining the instant position of said needle for developing a control signal, said means for permitting movement of said tracker plate being controllably associated with said means for determining and responsive to its output.
 8. An apparatus as claimed in claim 1, wherein each carriage member includes at least one pair of guide wheels mounted with their axes of rotation vertical and arranged to engage one on each side of the respective said guide means of said tracker plate to allow said carriage members to traverse the length of the respective said guide means.
 9. An apparatus as claimed in claim 1, wherein each said guide means on said tracker plate is provided with a plurality of notches and each said carriage member is provided with a respective switch member, the contacts of which are arranged to be closed whenever the respective switch member of a particular said carriage member is aligned with a notch on the respective one of said edges of said tracker plate.
 10. An apparatus as claimed in claim 9, wherein said first carriage member includes a main body portion pivotable between a raised and lowered position, this carriage member being provided with a further switch member whose contacts are actuated when the main portion of said first carriage member is raised or lowered.
 11. An apparatus as claimed in claim 9, wherein said switch members comprise first and second microswitches provided on said first and second carriage members respectively, said first and second microswitches being connected electrically in series and to a sequencing unit, which includes counting means arranged to be stepped sequentially in response to pulses generated each time contacts of said first and second microswitches are actuated upon alignment of said switches with notches in said guide means of said tracker plate.
 12. An apparatus as claimed in claim 11, including a further switch member, and wherein contacts of said further switch member are actuated whenever said tracker plate is in the correct position for commencement of a machine cycle, to complete a circuit to a sequencing unit to reset its counting means to the beginning of a counting cycle, said sequencing unit including a trigger delay circuit being repsonsive to the resetting of said sequencing unit to supply energizing current to a winding of a solenoid associated with said first carriage member, an arm connected to an armature of said solenoid retaining said first carriage member in its raised position and energization of said winding of said solenoid effecting actuation of said armature to actuate said arm and allow said first carriage member to move into engagement with said tracker plate.
 13. An apparatus as claimed in claim 12, wherein said winding of said solenoid is de-energized upon movement of said first carriage member and power is supplied to electromagnet clutch means associated with one of said gear assemblies.
 14. An apparatus as claimed in claim 13, including a plurality of electromagnetic clutches, and stepped counting means for supplying an output pulse via a matrix of a programme unit to a control means providing a preselected current path to at least one of said electromagnetic clutches of said gear assemblies to effect energization of the winding thereof and to cause a respective one of said pinions to be rotated to move the associated rack via one of said idle gears.
 15. An apparatus as claimed in claim 1, including a thread cutting device provided on said machine beneath the needle plate thereof, said device including a solenoid whose winding is energized in response to application of a brake to cut the thread and allow said tracker plate to be removed from the machine.
 16. An apparatus as claimed in claim 15, including means responsive to stopping of movement of said tracker plate to hold thread in said needle to allow saiD needle to be withdrawn from the workpiece without dethreading.
 17. A profile stitching apparatus as claimed in claim 1, wherein additional means, associated with said first and second transmission means, are provided for permitting movement of said tracker plate in timed relationship with the operation of said sewing machine such that said tracker plate is moved only when said needle is clear of a workpiece. 